1. Field of the Invention
The invention relates to an adapter for an assembly having a valve and a positioner, where the valve includes a first interface and the positioner includes a second interface corresponding thereto, which are each configured for tube-less and pipe-less connection of the valve to the positioner in accordance with the guideline VDI/VDE 3847.
2. Description of the Related Art
In order to control process valves, use is frequently made of pneumatic actuating drives (i.e., positioners), in which a diaphragm acting on an actuating element, such as on a closing element of a control valve, has pressure applied to it with the aid of a gaseous medium, for which in this application the general term “air” will be used, and is thus deflected. The application of a variable pressure to the diaphragm can be performed on one side, where the diaphragm is loaded by a spring on the other side, or it can be performed on both sides, with different pressures on the two sides of the diaphragm generating a drive force. The control of the pressures is performed via an electro-pneumatic position controller, in which an electrically actuated valve distributes feed air under pressure to the two sides of the diaphragm in the actuating drive via two air exhaust connections, depending on the activation.
EP 1 632 679 A1 discloses an electro-pneumatic position controller, in which a valve for distributing compressed air to two air exhaust connections can be employed in two different installation positions, where control air connections of the valve are each connected in an aligned manner to another of the two air exhaust connections in the two installation positions.
U.S. Pat. No. 6,354,327 B1 describes an assembly having an electro-pneumatic position controller and a pneumatic drive, in which a pneumatic switch is inserted between position controller and drive in order to permit a manual intervention.
The guideline VDI/VDE 3847 describes an additional interface between the drive of a positioner and position controller. Particular attention was directed to the mounting of the position controller being suitable for high vibration and shock loading and for pipe-less solenoid valve mounting in accordance with VDI/VDE 3845. The basis of the concept is the mounting of the position controller from the front on a vertical surface of the bonnet, which is provided with air ducts and fixing threads and a coding pin. Via the air ducts, both the feeding of the feed air and the connection to single-acting or double-acting drives are performed. As a result, replacement of the position controller is possible without disassembling existing feed air or control air lines. On the same side of the bonnet, at the back, a second vertical surface is provided, is likewise provided with air ducts and fixing threads and can also be used as a second interface for tube-less and pipe-less mounting of a solenoid valve. The connecting surfaces for the solenoid valve and position controller are optionally a fixed constituent part of the bonnet or can be implemented via a separate connecting block fixed to the bonnet. Since, in the aforementioned guideline, only the minimal size of the connecting surface, the position of the threaded holes, of a dowel pin and the inlet and outlet openings of air ducts are defined, but not a clearance which has to be provided in the area of the second interface for the mounting of the solenoid valve, there is the problem that, in the case of some drives, it is possible for a collision to occur between the solenoid valve and, for example, the head of the drive, if an attempt is made to mount the solenoid valve on the second interface when there is inadequate clearance.